Here you can see a shag skull from the top, now break the beak off along the 'hinge' that all phalacrocoracidae have at the base of the beak and there is a striking resemblance to the skull in question.

It is more difficult to do this with the under view of the skull because the skull in question is missing not only the beak but the palatine bones, pterigoids and quadrates.

Thanks Chris, these were the sort of photos I was looking for on Google. The skull on the skullsite is complete, Your skull is less complete and the skull which started this thread is even les complete. I think having your photos has provided the link